Determining zones of fluid flow in a well bore



Dec. 28, 1954 1', v, MOORE ETAL 2,697 941 DETERMINING'ZONES OF FLUIDFLOW IN A WELL BORE Filed Sept. 14, 1950 TEMPERATURE TEMPERRTUREMEAfiURING ELEM ENT FLOW MEASURING ELEMENT HEATING ELEMENT TE MPERATUREMEASURING ELEMENT ELEMENT Thomas V. moors Robert 12. 7720112 05012Gboorrleg' TEMPERATURE Msnsuemc ELEMENT s'lnv anoors United States P 25973, 4 nETERMmusG'zoNEsoF Lmfi mow-mm 5 WELL BORE .Thisxinvention(concerns a novel method toflprovide information as to thpoints ofentry; or ex t; of mild to or'Tfr'om a well bore: The appa'ratus'of thisinvention in' the simplestform cotnprises -a cable to be lowered into awell:boreysupportiiigatemperatureimeasuringaele= ment; and, displacedtherefrom a' heating element. By lowering thisrapparatus" downla boreholecin a'first step of the operation infiwliichF-th' heater: is not:operated and by them lowefin'g t'he" apparatus down 'the'bore --in' asecond ste'p'zofctheoperation' whilertheiheateriis' operated,- lntormation': is obtained asittoi' fluidfifl'ow' entering- ;or-rleav1ng the well' bore a'tipoint's alongthe= well: In apreferred em: bodiment'. of theinvention; .a at 'fiowvolume indicator 1s employed in combination?with". theindicated apparatus providing additional informationfielmlttlng-.thBldQllllfication of the fluid flow at points in the wellas an oil-gas flow or an oil-water flow. a

In the production oftiil from a suitable producing well, it isfrequently desirable to ascertain exactly where, and afhow'niariypointsj aIolng the Well; nujdmaype enterirfg are went Equally; 31313eis' information as to plii'g'g ing iori's' in he v ve11 w1i erewaterrather than oil may; enter." Agaimi e casie of-awellfbore winchhasbeen 4O caseili itis often e cssa'r 'y todeterm e{ a Forthese and'otherpurposesythemet v i s provided.- While; as"indicated,= theprimary istodetermine pointsot the well atwhih fluiql o'r "leaves-tile well;aswill be apparent,- th' '11- v ea has oth gapp ications such as locatingfleaksin welt tubing of easing, etc:

aecordaii e withing invention conditions -in a; w llare cehtrlled so'a's to niamtamaconstantra f fi t,

A temperature' eed aiiig e'rjjadgegigg ow'r'dfi b the We a dz re h' tzllr adhewellg or is coninstruiiie'rit'rnaybe of-s'uch a natureas to recordperature 011a chart previaed imne ownfthe h 'lefp ofth'e" apparatus.Fo're'XampleQ alli with a" re ording pmmay be empl d f or thfilterriativel'y} and-preferabl a temperatu element, such as aresistance thermome display th v'a ria ions depth 'asthe apparatus -1sand heating element is* prov ded atefiff) See Wellfluids'tbyttheme'ater; Sinceithetehiperaturesrecordedi by: thetemperature. measuring means: will: be a functione of the" amount of'ifluid-'passingthe heating element prior to' contacting-tthe-ztemperature measuringlmeans; it is thus- 1 possible to determinevariations in' the quantity. of fluidflow:atzdifiei'ent points in thewell; For example, -if-/su'b-' stantially all fluid? flow; in" the 1well is produced' at a given zone A and little=fluidflow is'producedbelow'zone-A,I upon" ltzwvering thev temperature'measuringl and heatingelements through and below zone A; a sharp in'cr'e'a'se in temperature'will beobserved; In'a simple situation of" this type; it'may be: notedthat the desired 1 information: as" to 1 fluid How may be obtainedwithout necessity for the control run conducted with the-temperatureiiieasura ing element alone. However;- preparation of the two curvesshowing I the temperature depth relation with: and without heateroperationais a" particular feature-of this invention intended todetermine, for: eXampIepte'mPei a-Q ture "anomalies caused'by expansion"and cooling ofigases released in the wellt.

In a preferred embodiment of this inventionbthe at)? paratustdes'cribedis supplemented byemploying; in com bination therewith,la velocity offlow indicator By' employi'ng the-flow indicator to'pro'videinformationas tothe volume' 'o' f we'll-fluids" passing the heaterandtempera ture' measuringmeans, it is possible to difierentiatebe tweenentry of 'o ilgtgasg orwat'er into thewel-l;

This invention'may be more fully understood by rdf erence to thefollowing description drawn in conn'eetidn with the'accotnpa'nyingdrawings in which:

Figure '1 diagra'mmaitieally indicates the simplest "form" of-apparatus: for practicinggthis inventibnywhilet Figure I 2 iliustratesatypical plotof" the dataobtained withtheapparatusofFigure 1; and: I

Figure 3 diagrammatically indic'a'te'safurtherertibodimen'tof'theapparatus ofthis invention-employing'th mometers both aboveand below the heating element, in" combination with" a flow velocityindicator. v

Re't'erririg now to the drawings; the numeral; 1 indicates a well borenomwhwmt is assumed wen fluids" arerio duced. in practicing thisinvention; it isnec'es's'ar'y that tubing inthewellibe removed or raisedabove the pertionofthe well" to be surveyed. It ispreferred; that atleastthe upper: portion otthe" well be provided with" a casing? whichmay be cemented-in thewell'by meansof the cement" 3; The casing is'provided with asui't able capping element 4 provided with a fluiddischarge line s equipped with a valve 6 to permit control of the rateat which fluid flows from-tlie-wellt As indicated, in the practice ofthis invention; vaive 6 is maintained at a suitable setting so as topermit a constant and slow ii of fluid from the well duringth'e'temperatureidternii operations; for example, valve 6 maybe s'et' tdp aconstant flow of Well fluid of about 5 ba'rrels'pe'r hour; The apparatusillustrated is theh low'ered' in'to"'the" Well" on cable] through asuitablepack'in'g gland or st'ufling M708: T he required': apparatusco'nsists'of a temperature determining element 9 positioned' somedistance on the cable above-a heating element 10'; It isparticularlypreferred: that the temperature determining flrne'ans 9"consist of'a resistance thermometer,- or the like; capable ofprovidingelectrical signals Whiclrniay be car'ried 'to'th'e' surface of the earththrough electrical conductors provided in the cable 7. Cable 7 atthesilrfacebf the;

' earth is -pass'ed over a measuring wheel 11 or conventional characterto provide a-continuousplot of thedep'th. to which the apparatus hasbeen lowered inithef-well Cable 7 ma be' wound on a" drum or relflZ-provided with suitable slip" rings and sliding contactsficontairied'within box. 13 so as to establish contactbetweeii therends of theconductors within cable 7 f and recorder 14", so that theele'ctricalsignals producedby temperature nieas uring means" 9' may" be recordedRecorder" 14 is co'nnected to the "appropriate 'term'inalsof box 13bymeans' of conductors. 161 in addition-to 'these apparatus ele;nient's, it is necessary that means he provided to: supplya suitableheatingcurrent thre gh'ceriductersidt theca 1e? 7 .tooperateithe-.heater 10: This current may be, Suppl throu'glrconductors17 a suitable source. f Suita' therammin chart within Reorder 14 .1iiayfb'etilri; tent directly by the measuring wheel 11 through shaft orcoupling 21 so its motion will be directly proportional to the depth ofthe apparatus in the bore hole.

In employing this apparatus, it is preferred that a first run be made inwhich the apparatus is lowered into the well, while the heater isinoperative. In this case, as shown in Figure 2, a temperature depthcurve may be plotted showing the variation in temperature with depthunder the normal conditions existent in the well. In general, asillustrated by curve A of Figure 2, such a curve will be substantiallylinear showing a continuous increase in the temperature of the wellfluids as the depth down the well is increased. However, certainirregularities are to be expected in such a curve, due for example tointroduction into the well of gases which upon expanding in the well mayproduce cooling effects. Again, large influx of well fluids atparticular points of the well may cause curve A to be nonlinear.

A- second run is then made in which all conditions are maintained thesame except that the heater 10 is operated while the apparatus islowered into the well. The particular quantity of heat supplied byheater 10 is only critical in the sense that a constant amount of heatmust be supplied capable of substantially heating the fluid in the wellso as to provide a readily discernible increase in the fluid temperatureat the rate of flows maintained. Thus, for example, if it be assumedthat a flow of 5 barrels per hour is maintained in a well bore 6 inchesin diameter, and if it be assumed that the specific heat of the fluid isabout 0.5 then a 500 watt heater would raise the temperature of thefluid about 2 F in passing the heater. As it is of .course necessary tomeasure the temperature rise resulting from the operation of the heaterwith reasonable accuracy, it is thus important that heater 10 be capableof providing about this increase in temperature. Consequently, while asuitable heating element 10 is operating, a second run is made toprepare a curve such as curve B shown in Figure 2. In general, asillustrated, curve B will parallel curve A, differing therefrom by atemperature equal to the heating effect on the quantity of fluid passingthe heater and temperature measuring means in the well. However, atpoints in the well immediately below zones at which fluid flows into thewell, increases in temperature will be observed such as at points and 16of curve B. These temperature fluctuations will occur since at thesepoints in the well, as the apparatus is lowered, a decrease in thevolume of fluid flow will be encountered causing the fluid to be heatedto a higher temperature by the heating element.

This effect may be understood by reference to the following equation:

E=heat supplied, B. t. u./ min. k=specific heat of fluid, B. t. u./ cu.ft. A=cross section of hole, sq. ft. V =velocity of flow, ft./min.

in which delta T indicates the amount of temperature rise; E equals theheat supplied, expressed inv B. t. u.s per minute; k equals the specificheat of the fluid in B. t. u.s per cubic foot; A equals the crosssection of the hole in square feet, and V equals the velocity of flow infeet per minute. Referring to this equation, it will be noted that E andA in any particular run will be substantially constant and that K mayalso be considered to be substantially constant. Consequently, theamount of temperature rise appreciated at different points in the wellwill be a function of the velocity of fluid flow past the heatingelement and the thermometer. For this reason variations of curve B notdisplayed by curve A will indicate points of the well at which fluidsare flowing into the well.

Referring now to Figure 3 a somewhat different embodiment oftheapparatus employed is illustrated. In this embodiment, a secondtemperature measuring means 20 is maintained below heater 10 andtemperature measuring means 9. By employing the apparatus of Figure 3,essentially the same information provided in Figure 2 may be obtained ina single run of the apparatus down the well bore. Employing theapparatus of Figure 3, temperature measuring means 20, since it ispositioned below heater 10, will provide curve A shown in Figure 2.Temperature measuring means 9'by'virtue'of the heating effect of heater10 will provide the information shown by curve B of Figure 2. Inemploying the apparatus of Flgure 3, it is convenient to electricallyconnect temperature measuring means 9 and 20 so that the differentialell) temperature determined by the two may be plotted. In this case asingle curve of differential temperature vs. depth may be preparedessentially showing the difference in temperatures between curves A andB of Figure 2. On such a curve, variations in the temperaturedifferential with depth will indicate points at which fluid enters thewell bore.

As an optional, although preferred feature, the apparatus of Figure 3includes a flow-volume measuring means indicated by the numeral 25. Thiselement of the apparatus may be chosen from those known to the art of acharacter to develop electrical signals characteristic of the fluidflow. For example, element 25 may consist of a spinning member, actuatedby the fluid flow, which will operate a small generator to provide anelectrical output proportional to the volumetric flow. It is convenientto employ this type of flow indicator which develops an A. C. voltage asthis voltage may be impressed on conductors of cable 7 carrying the D.C. voltage of either of the temperature measuring elements. As known,the D. C. and A. C. signals may be separately recorded at the surface ofthe earth.

The complete apparatus of Figure 3 therefore provides information as tothe temperature increase (AT) appreciated by operation of the heaterunder the flow conditions existing at different depths in the well andalso gives at least an approximation of the velocity of fluid flow orthe volumetric flow rate. Use of this information is indicated by thefollowing formula:

E av? where E is the heat supplied by the heating element expressed inB. t. u.s per minute, C is the specific heat of the fluid flowing pastthe heater expressed in B. t. u.s per pound, W is the weight of fluidpassing the heater expressed in pounds per minute and AT is theresultant temperature rise or the differential temperature of the twotemperature measuring means of Figure 3. Assuming that the fluid passingthe heater consists substantially of hydrocarbons, W may be computedsince the specific heat of all hydrocarbons present in a well isapproximately the same. As the apparatus described provides informationas to the volume of flow, by dividing the computed weight by the volume,the apparent density of the fluid will be obtained, so as to indicatewhether the hydrocarbon flow is in liquid or gas phase at particularpoints in the well.

The computations indicated above to distinguish between flow of oil orflow of gas into the well are of course not valid if water issimultaneously flowing into the Well. It may be noted, however, that oiland gas or oil and water may be produced in a given well, but generallyall three are not. In the event a particular well being surveyed isproducing both oil and water, points of water production may readily beidentified by comparing the AT information with the volume of flowinformation. Since the specific heat of water is approximately twicethat of hydrocarbons, points of water entrywill be indicated whereverdecreases in AT are disproportionate to increases in the volume of fluidflowing.

By this means, therefore, the embodiment of the invention illustrated inFigure 3 is adapted to indicate the nature of the fluid entering thewell in addition to the points of fluid entry.

The spacing of thermometer 9 from heater 10 is critical in the practiceof this invention. It is necessary that elements 9 and 10 besufliciently displaced so that normal heat diffusion through the wellfluids will not affect temperature measuring means 9 under theconditions of fluid flow and at the rate at which the apparatus islowered. For this reason elements 9 and 10 should be displaced on cable7 by at least about 1 to 3 feet. This same limitation applies to theplacement of measuring means 20 below the heating element 10. Baffles 28may well be positioned between the heater and the temperature measuringmeans to minimize possible diffusion effects and to provide sufficientmixing action to eliminate any crosssectional temperature differentialsin the fluid adjacent the temperature measuring means. While, asindicated,

the apparatus described may be employed by sequentially lowering theapparatus to successively lower points in the well, it is preferred thatthe apparatus be employed by lowering the apparatus slowly down the wellat a constant rate.

It is apparent that the general process and apparatus described may bevaried to secure different objectives. For example, in the case in whichit is desired to determine leaks in a completely cased hole, the samegeneral principles described may be applied. In this case operation maybe conducted while exerting a constant pressure on the well hole eitherby maintaining a constant flow of well fluids, or by maintaining no moreflow than required to keep the pressure constant.

Again, while the process has been described with reference totemperature determinations made while the apparatus is lowered in thewell, it is apparent that the process may be conducted while theapparatus is raised to the surface.

What is claimed is:

l. A process for determining zones of fluid flow into and out of a wellbore producing fiuids which comprises the steps of controlling the flowof fluids out of the well bore at a selected constant low rate of flow,measuring and recording the temperatures existing at various depthswithin the well in a first vertical traverse through the well, supplyinga constant known heating efliect at various depths within the wellduring a second vertical traverse through the well, and measuring andrecording the temperatures existing at various depths in the well at afixed distance behind the point at which the said constant heatingeffect is supplied, whereby points of fluid entry and fluid egress alongthe well bore may be determined as indicated by appreciable variationsin the normal temperature differential between thetemperature-versusdepth plots for the two traverses at particularindicated depths within the well bore.

2. Process as defined by claim 1 including the step of simultaneouslymeasuring and recording, during said sec ond traverse, the rate ofvertical flow of fluid within the well bore at various depths within thewell at a fixed distance behind the point at which said constant heatingeffect is supplied, whereby the nature of the fluids flowing into andout of the well at particular depths may be determined by comparison ofthe measured vertical flow rates and the measured temperaturedifferences at said particular depths within the well bore.

3. Process as defined by claim 1 wherein said first and second traversesare combined by measuring and recording the temperatures existing atvarious depths within the well, supplying a constant known heatingeffect at various depths within the well at a point behind the point ofsaid first temperature measurement, and measuring and recording thetemperatures existing at various depths in the well at a fixed distancebehind the point at which the said constant heating effect is supplied.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,311,757 Jakosky Feb. 23, 1943 2,334,920 Gosline et al. Nov.23, 1943 2,342,827 Ackers Feb. 29, 1944 2,383,455 Abadie Aug. 28, 1945

